ZooL.— Vol. II.] EISEN—OLJGOCHMTA. 203 



The hidden nature of the sperm-ducts is characteristic of 

 both species of Trigastcr. This character is also found in 

 two species of Diplocardia but to a lesser degree, the ducts 

 being merely covered by the peritoneum or by a strand or 

 two of muscles. In the absence of diverticles of the intes- 

 tine Trigaster resembles the other genera of this family. 

 This character seems to me to be of the greatest importance 

 and I consider it to be the distinguishing feature between 

 Diplocardinae and Benhamin£e. 



The two species of Trigaster may be distinguished as 

 follows : — 



Trigaster tolteca, two gizzards, in V and VI. 

 Trigaster Lankesteri, three gizzards, in VII, VIII and IX. 



Trigaster tolteca, sp. nov. 



Plate XIV, Fig. 179. 



Definition. — Length over 120 mm., width below clitellum 5 mm., at the 

 tail 9 mm. Somites 190. Setae in couples, the ventral ones closer than the 

 dorsal. Penial setae at the prostates curved and smooth. Prostomium barely 

 indentates somite I. Dorsal pores posterior to clitellum. Clitellum in 

 XIII-XIX. Genital zone almost square, sunk, with two parallel fossae. A 

 small median papilla on XX. Two gizzards in V and VI. No diverticles of 

 the intestine. Very small septal glands extending to somite IX. Small sub- 

 pharyngeal glands present. Racemose sperm-sacs in XII growing out from 

 the dorsal vessel. Spermathecse without diverticles, in VIII and IX; the 

 pores in the intersegmental grooves VII/VIII, VIII/IX, postseptal. Testes 

 and sperm-funnels in X and XL Ovaries in XIII. Sperm-ducts hidden in 

 the longitudinal muscular layer of the body-wall, fusing at the pores in XVIII. 

 Prostates tubular, in XVII and XIX. Nephridia consist of many isolated 

 tufts, commencing in III. Dorsal vessel double in X, XI, XII (?). Hearts 

 very muscular, the last one in XIII. Color pale; no pigment. 



Septal formula: — 



V/VI, VI/VII, VII/VIII, VIII/IX, IX/X, X/XI, XI/XII, XII/XIII, 

 XIII/XIV. 



Habitat. — Toluca, Mexico, in the pine-region at an alti- 

 tude of 8,000. Collected by Professor Albert Koebele. 



Of the single specimen one-half of the anterior end was 

 sectioned lengthwise, the other half crosswise. The part 

 sectioned longitudinally exhibits the following anomaly: 



